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Carbon in the Atmosphere: Concentration Matters, Not the Source

Carbon emissions from different forms of energy should be judged based on the atmospheric impact and not on the source, according to an opinion piece published this month in the journal Global Change Biology.

The opinion piece was written in response to criticisms of the Biomass Sustainability and Carbon Policy Study that Manomet produced in 2010 for the Commonwealth of Massachusetts. That study found that burning woody biomass for electricity could initially produce more carbon emissions than using fossil fuels to produce the same amount of electricity.

Some critics have said that the study did not take into the account whether the carbon emissions come from biogenic (live plants) or geologic (beneath ground) sources.

“The physics of the greenhouse gas effect is indifferent as to the origin of the pollutant. Once a molecule of CO2 is in the atmosphere its heating capacity is the same regardless of its source,” according to the article. “If alternatives to fossil fuels include use of forest where carbon is emitted and resides in the atmosphere for long periods of time (e.g. decades or longer), a reduction of atmospheric concentrations of CO2 … will be difficult to achieve and may contribute to some degree of irreversible climate change.”

The article was co-authored by Manomet forest ecologist John Gunn, who was also a contributor to the 2010 study. The other authors on the paper were David Ganz, a Bangkok-based ecologist working on lowering emissions from Asia’s forests, and William Keeton, a forest ecology professor at the University of Vermont.

In an interview, Gunn said that the main point of the opinion piece is that climate policy must be driven by an understanding of emissions contributions to the atmosphere, and it is irrelevant if the carbon “is from a tree or a dinosaur.”

The debate “is a distraction from the bigger issue, we have to reduce concentrations of atmospheric carbon,” Gunn said. “CO2 is CO2, we can ‘t make this false distinction.”

Anyone interested in learning more about the issue or reading the full opinion piece should contact Gunn by email at jgunn@manomet.org.